全文获取类型
收费全文 | 647篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 22篇 |
综合类 | 1篇 |
化学工业 | 183篇 |
金属工艺 | 11篇 |
机械仪表 | 27篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 80篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 53篇 |
一般工业技术 | 105篇 |
冶金工业 | 50篇 |
原子能技术 | 17篇 |
自动化技术 | 87篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 51篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 46篇 |
2012年 | 28篇 |
2011年 | 48篇 |
2010年 | 38篇 |
2009年 | 23篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 22篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有680条查询结果,搜索用时 375 毫秒
91.
Liquid–liquid and vapor–liquid phase equilibria for the binary, ternary, and quaternary systems of vinyl acetate, surfactant, water, and poly(vinyl acetate) (PVAc) were obtained using liquid–liquid equilibria, inverse gas chromatography, and the headspace methods. The Flory–Huggins interaction parameters for the different species in the emulsion polymerization of PVAc latices are reported. These parameters could not be used to predict the phase equilibria because of their strong dependence on concentration. The UNIFAC‐vdW‐FV model was applied to predict the vapor–liquid equilibria in the binary and ternary systems containing vinyl acetate, 4‐nonylphenol polyethoxilate surfactant, and PVAc. The predicted results compare favorably with the experimental data for all systems. Diffusion coefficients were also measured for the solvents in the PVAc. Analysis confirmed that the diffusion in the latex particles was so fast compared to the reaction that the assumption of uniform monomer composition through the particles was valid. On the other hand, the results indicate that the complex thermodynamic interactions will lead to changes with time in the monomer concentration in the reacting polymer phase. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
92.
Wiesel O Tóth IE Boldogkoi Z Hornyák A Bokor V Halász B Gerendai I 《Microscopy research and technique》2004,63(4):244-252
Using the transneuronal viral tracing method, the central nervous system (CNS) connections of the uterine horn were studied in virgin, pregnant, and in lactating rats. The frequency of viral labeling in the brain and the distribution of virus-infected neurons from the uterine horn were compared among groups. There was a marked difference in the frequency of viral labeling in the brain stem. In virgin rats more than half of the brain stems (5 out of 9) were labeled. In contrast, in pregnant animals viral-labeled neurons were detected in only a few cases (3 out of 16) and almost each brain stem of the lactating group was labeled (12 out of 13). A similar, less marked difference was observed in the hypothalamus. The pattern of distribution of infected neurons was similar in each group. In the brain stem, the nucleus of the solitary tract, dorsal motor nucleus of the vagus, area postrema, gigantocellular and paragigantocellular nucleus, ventrolateral medulla, A5 cell group, and caudal raphe nuclei were the most frequently labeled structures. In the diencephalon, viral-infected neurons were detected primarily in the hypothalamic paraventricular nucleus. The telencephalon was devoid of infected cells. Data suggest that the CNS control of the uterine horn varies depending on reproductive status. The low frequency of brain labeling in pregnant rats may be related to the almost complete lack of sympathetic fibers in the uterus prior to parturition and the very high frequency of labeling in lactating animals to the postpartum hyperinnervation of the uterus. 相似文献
93.
The electrical properties of single phenylene oligomers were studied in terms of the dependence of the tunneling current on the length of the oligomers using self-assembling techniques and scanning tunneling microscopy (STM). It is important to isolate single molecules in an insulating matrix for the measurement of the conductivity of the single molecule. We demonstrate here a novel self-assembled monolayer (SAM) matrix appropriate for isolation of the single molecules. A bicyclo[2.2.2]octane derivative was used for a SAM matrix, in which the single molecules were inserted at molecular lattice defects. The isolated single molecules of phenylene oligomers inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights of the molecular protrusions using STM and estimated the decay constant, beta, of the tunneling current through the single phenylene oligomers using a bilayer tunnel junction model. 相似文献
94.
We investigate resource allocation concerning the provision of cross- border transport infrastructure, which is used for trade
of goods between two neighboring countries. Since the level of infrastructure is sub-optimal under the circumstances that
two governments choose the levels of infrastructure independently, we focus on the role of foreign aid to improve the efficiency
of infrastructure provision. In this paper, we examine the welfare effects of aid policies, and show that aid can make both
countries better off, i.e., Pareto improvement. Furthermore, Pareto improvement is more likely if the stage of development
in recipient country is very low or sufficiently high. 相似文献
95.
Well size-controlled copper fine particles (diameter: 100-300?nm) were used as the inner electrode material of multilayered ceramic capacitors (MLCCs). The particles were dispersed in terpineol to form a printing paste with 50?wt% copper particles. The MLCC precursor modules prepared by the layer-by-layer printing of copper and BaTiO(3) particles were cosintered. Detailed observation of the particles, paste, and MLCCs before and after sintering was carried out by electron microscopy. The sintering temperature of Cu-MLCC was as low as 960?°C. The permittivity of these MLCCs was successfully measured with the copper inner layers. 相似文献
96.
Tomonari M Ida K Yamashita H Yonezawa T 《Journal of nanoscience and nanotechnology》2008,8(5):2468-2471
Size-controlled oxidation-resistant copper fine particles were prepared from insoluble CuO micron-sized particles. The particle sizes were quite uniform and could be varied only by the concentration of the complex reagent from 45 to 175 nm. No template material was needed for size control. Gelatin was selected as the protective polymer. Addition of protease after formation of copper fine particles decomposed preferentially loop and tail parts of gelatin. The remaining nanoskin gelatin layer, covered on the particle surface, prevents oxidation of copper. 相似文献
97.
This paper briefly summarizes a laboratory study investigating strategies designed to improve the ability of our most vulnerable drivers, the elderly, to safely negotiate the most dangerous and demanding of all traffic situations--intersections--through increased use of modern roundabouts. Compared to conventional intersections, roundabouts have demonstrated the potential to significantly reduce the most injurious (angle) type of crashes and slow the operating speed of all vehicles, while maintaining a high capacity for moving traffic through an intersection. This research sought to develop and evaluate countermeasures with the potential to improve the perceived comfort, confidence, and/or safety of seniors in using roundabouts. Research methods included focus groups and structured interviews utilizing photographs, which had been edited to include novel traffic control devices. The results suggest that design elements that improve the path guidance for older drivers are necessary to encourage roundabout use by this group. Recommendations for improved practice related to advance warning signs, guide signs, yield treatments, directional signs, and exit treatments are presented. 相似文献
98.
Rahman NM Iida T Yamazawa H Yokoyama S Moriizumi J Saito F Ito T 《Radiation protection dosimetry》2007,124(4):360-371
The indoor workplace environment was evaluated for exposure to radon and its decay products at two Universities in two metropolises of Japan. The mean radon concentrations in Nagoya University (NU) and Hokkaido University (HU) were 16.7 Bq m(-3) and 18.0 Bq m(-3), respectively. Activity median aerodynamic diameter (AMAD) of particles at NU ranged from 172 nm approximately 205 nm and at HU from 186 nm approximately 300 nm. Estimated effective doses for five usual sites of NU by ICRP approach was 0.15 mSvy(-1) approximately 0.76 mSvy(-1) and by UNSCEAR approach was 0.05 mSvy(-1) approximately 0.24 mSvy(-1). The effective dose for the same of HU by ICRP 66 approach was 0.16 mSvy(-1) approximately 0.79 mSvy(-1) and by UNSCEAR 2000 approach was 0.05 mSv y(-1) to 0.26 mSv y(-1). The two approaches differs on an average by a factor 2.3- approximately 4.7. The AMAD of obtained particle size distribution at NU has an average total deposition of 23% in human respiratory tract and 20% at HU. 相似文献
99.
In a previous study, statistical method using two distributions was applied to analyze detergency of oily soil. The method uses statistical distributions of detergent power and adhesive force of soil. In this paper, this method was applied to an analysis of detergency of solid particles. Soiled cotton cloth was prepared with red iron oxide dispersion liquid in Terg-O-Tometer. Four-time consecutive washings tests were conducted with dodecyl sulfuric acid sodium salt (SDS) and alcohol ethoxylate (AE) aqueous solutions in Terg-O-Tometer. Change of removal efficiencies due to repetitive washing was utilized to seek the two distributions. Predicted removal efficiencies calculated from computer simulation corresponded to experimental values. Different adhered states of soil, prepared by varying soiling conditions, were expressed as Removal Resistance. As soiling mechanical power increased, Removal Resistance shifted toward higher adhesive force of soil and an amount of soil had also increased. Iron oxide concentration only had an affect on an amount of soil. The results showed that the method using two statistical distributions can be applied to the detergency of solid particle. 相似文献